1. Field of the Invention
The present invention relates to a power amplifier module having a bias circuit with improved linear characteristics.
2. Description of the Related Art
A hybrid bipolar transistor (HBT)-based power amplifier, most commonly used in the field of RF communications, has been known as an amplifier satisfying both high efficiency and linear characteristics.
In addition, a large portion of RF communications equipment has been integrated by using complementary metal oxide semiconductor (CMOS) process technology and studies into CMOS process-based power amplifiers have been actively ongoing due to low unit costs and the advantages of a multi-chip structure.
However, despite these advantages, CMOS power amplifiers have been difficult to commercialize as compared with HBT-based power amplifiers. This is the result of low insulation voltages, large source grounding lead inductances generated due to the absence of a via process, and a deterioration in the physical performance of a conductive substrate.
To address these physical limitations, there is a need of the provision of a bias circuit capable of actively supplying a bias power to the CMOS power amplifier to improve linear characteristics.